The grass density in the viewport is not real, it is limited by the Display->Viewport->Max Items value. For this scene a distribution map's size of about 1000 inches should be enough.
Please, try a render using a distribution map scale of 1000". You also would set a higher value for Display->Max Items (as 200K items or more) to see the result in the viewport.
If that helps, i have attached a grass scene using a similar setup (Max 9, VRay).